WASHINGTON, D.C. — The White House has sunk to an all-time low by telling hundreds of black voters in Virginia that Republicans would put them "back in chains," Republican presidential candidate Mitt Romney says.

Vice-president Joe Biden made the seemingly racially charged remarks at a campaign stop in Danville, Va., Tuesday. He warned the crowd, which included several hundred African Americans, that Romney and his running mate Paul Ryan want to "unchain Wall Street" but their economic policies would "put y'all back in chains."

Speaking to CBS Wednesday morning, Romney blasted President Barack Obama's re-election team for pursuing a campaign of "hatred" and "division."

"These personal attacks, I think, are demeaning to the office of the White House and the comments yesterday by the vice-president just diminish the White House that much more," Romney said. "Comments of this nature sink the White House just a little lower. The American people expect something better from the president than these kinds of divisive comments."

While he hasn't apologized, Biden did later try to clarify his remarks, saying he should have used the term "unshackled" instead, since that is the very term Ryan once used to describe what he and Romney think should be done to the U.S. economy, to free it from what they see as overly burdensome government regulations to help it recover more quickly.

Republicans, though, aren't buying Biden's explanation.

Former New York mayor and one-time Republican leadership candidate Rudy Giuliani even questioned Biden's mental capabilities, saying Tuesday's gaffe is but the latest for Obama's No. 2 man.

"The vice-president of the United States has become a laugh line on late night television. I mean, I've never seen a vice-president that has made as many mistakes, said as many stupid things," Giuliani reportedly said Tuesday night. "I mean, there's a real fear if, God forbid, he ever had to be entrusted with the presidency, whether he really has the mental capacity to handle it.

"I mean, this guy just isn't bright. He's never been bright. He isn't bright. And people think, 'Well, he just talks a little too much.' Actually, he's just not very smart."

The Obama campaign is doubling down on the attack, saying the Republicans' outrage at Biden is misguided. What is outrageous, Biden said later Tuesday, is the economic platform of the Republicans that would lower taxes for the wealthiest Americans and raise taxes on the middle class.